diff --git a/clippy_lints/src/deprecated_lints.rs b/clippy_lints/src/deprecated_lints.rs index 1c3285ed701..bec0c9f93a0 100644 --- a/clippy_lints/src/deprecated_lints.rs +++ b/clippy_lints/src/deprecated_lints.rs @@ -51,26 +51,6 @@ declare_deprecated_lint! { "`Vec::as_mut_slice` has been stabilized in 1.7" } -declare_deprecated_lint! { - /// **What it does:** Nothing. This lint has been deprecated. - /// - /// **Deprecation reason:** This used to check for `.to_string()` method calls on values - /// of type `&str`. This is not unidiomatic and with specialization coming, `to_string` could be - /// specialized to be as efficient as `to_owned`. - pub STR_TO_STRING, - "using `str::to_string` is common even today and specialization will likely happen soon" -} - -declare_deprecated_lint! { - /// **What it does:** Nothing. This lint has been deprecated. - /// - /// **Deprecation reason:** This used to check for `.to_string()` method calls on values - /// of type `String`. This is not unidiomatic and with specialization coming, `to_string` could be - /// specialized to be as efficient as `clone`. - pub STRING_TO_STRING, - "using `string::to_string` is common even today and specialization will likely happen soon" -} - declare_deprecated_lint! { /// **What it does:** Nothing. This lint has been deprecated. /// diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 866dae110cc..67a3a3fcf48 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -441,14 +441,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: "clippy::unstable_as_mut_slice", "`Vec::as_mut_slice` has been stabilized in 1.7", ); - store.register_removed( - "clippy::str_to_string", - "using `str::to_string` is common even today and specialization will likely happen soon", - ); - store.register_removed( - "clippy::string_to_string", - "using `string::to_string` is common even today and specialization will likely happen soon", - ); store.register_removed( "clippy::misaligned_transmute", "this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr", @@ -840,6 +832,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: &strings::STRING_ADD_ASSIGN, &strings::STRING_FROM_UTF8_AS_BYTES, &strings::STRING_LIT_AS_BYTES, + &strings::STRING_TO_STRING, + &strings::STR_TO_STRING, &suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL, &suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL, &swap::ALMOST_SWAPPED, @@ -1186,6 +1180,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: store.register_early_pass(|| box asm_syntax::InlineAsmX86AttSyntax); store.register_early_pass(|| box asm_syntax::InlineAsmX86IntelSyntax); store.register_late_pass(|| box undropped_manually_drops::UndroppedManuallyDrops); + store.register_late_pass(|| box strings::StrToString); + store.register_late_pass(|| box strings::StringToString); store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![ @@ -1228,6 +1224,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&shadow::SHADOW_REUSE), LintId::of(&shadow::SHADOW_SAME), LintId::of(&strings::STRING_ADD), + LintId::of(&strings::STRING_TO_STRING), + LintId::of(&strings::STR_TO_STRING), LintId::of(&types::RC_BUFFER), LintId::of(&unwrap_in_result::UNWRAP_IN_RESULT), LintId::of(&verbose_file_reads::VERBOSE_FILE_READS), @@ -1943,14 +1941,6 @@ fn register_removed_non_tool_lints(store: &mut rustc_lint::LintStore) { "unstable_as_mut_slice", "`Vec::as_mut_slice` has been stabilized in 1.7", ); - store.register_removed( - "str_to_string", - "using `str::to_string` is common even today and specialization will likely happen soon", - ); - store.register_removed( - "string_to_string", - "using `string::to_string` is common even today and specialization will likely happen soon", - ); store.register_removed( "misaligned_transmute", "this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr", diff --git a/clippy_lints/src/strings.rs b/clippy_lints/src/strings.rs index ede37624f71..42c45be3b45 100644 --- a/clippy_lints/src/strings.rs +++ b/clippy_lints/src/strings.rs @@ -2,6 +2,7 @@ use rustc_errors::Applicability; use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, LangItem, QPath}; use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_middle::lint::in_external_macro; +use rustc_middle::ty; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Spanned; use rustc_span::sym; @@ -11,7 +12,7 @@ use if_chain::if_chain; use crate::utils::SpanlessEq; use crate::utils::{ get_parent_expr, is_allowed, is_type_diagnostic_item, match_function_call, method_calls, paths, span_lint, - span_lint_and_sugg, + span_lint_and_help, span_lint_and_sugg, }; declare_clippy_lint! { @@ -289,3 +290,100 @@ impl<'tcx> LateLintPass<'tcx> for StringLitAsBytes { } } } + +declare_clippy_lint! { + /// **What it does:** This lint checks for `.to_string()` method calls on values of type `&str`. + /// + /// **Why is this bad?** The `to_string` method is also used on other types to convert them to a string. + /// When called on a `&str` it turns the `&str` into the owned variant `String`, which can be better + /// expressed with `.to_owned()`. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// + /// ```rust + /// // example code where clippy issues a warning + /// let _ = "str".to_string(); + /// ``` + /// Use instead: + /// ```rust + /// // example code which does not raise clippy warning + /// let _ = "str".to_owned(); + /// ``` + pub STR_TO_STRING, + restriction, + "using `to_string()` on a `&str`, which should be `to_owned()`" +} + +declare_lint_pass!(StrToString => [STR_TO_STRING]); + +impl LateLintPass<'_> for StrToString { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) { + if_chain! { + if let ExprKind::MethodCall(path, _, args, _) = &expr.kind; + if path.ident.name == sym!(to_string); + let ty = cx.typeck_results().expr_ty(&args[0]); + if let ty::Ref(_, ty, ..) = ty.kind(); + if *ty.kind() == ty::Str; + then { + span_lint_and_help( + cx, + STR_TO_STRING, + expr.span, + "`to_string()` called on a `&str`", + None, + "consider using `.to_owned()`", + ); + } + } + } +} + +declare_clippy_lint! { + /// **What it does:** This lint checks for `.to_string()` method calls on values of type `String`. + /// + /// **Why is this bad?** The `to_string` method is also used on other types to convert them to a string. + /// When called on a `String` it only clones the `String`, which can be better expressed with `.clone()`. + /// **Known problems:** None. + /// + /// **Example:** + /// + /// ```rust + /// // example code where clippy issues a warning + /// let msg = String::from("Hello World"); + /// let _ = msg.to_string(); + /// ``` + /// Use instead: + /// ```rust + /// // example code which does not raise clippy warning + /// let msg = String::from("Hello World"); + /// let _ = msg.clone(); + /// ``` + pub STRING_TO_STRING, + restriction, + "using `to_string()` on a `String`, which should be `clone()`" +} + +declare_lint_pass!(StringToString => [STRING_TO_STRING]); + +impl LateLintPass<'_> for StringToString { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) { + if_chain! { + if let ExprKind::MethodCall(path, _, args, _) = &expr.kind; + if path.ident.name == sym!(to_string); + let ty = cx.typeck_results().expr_ty(&args[0]); + if is_type_diagnostic_item(cx, ty, sym!(string_type)); + then { + span_lint_and_help( + cx, + STRING_TO_STRING, + expr.span, + "`to_string()` called on a `String`", + None, + "consider using `.clone()`", + ); + } + } + } +} diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index 1d906d20ad4..a104f687bdf 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -2237,6 +2237,13 @@ vec![ deprecation: None, module: "stable_sort_primitive", }, + Lint { + name: "str_to_string", + group: "restriction", + desc: "using `to_string()` on a `&str`, which should be `to_owned()`", + deprecation: None, + module: "strings", + }, Lint { name: "string_add", group: "restriction", @@ -2272,6 +2279,13 @@ vec![ deprecation: None, module: "strings", }, + Lint { + name: "string_to_string", + group: "restriction", + desc: "using `to_string()` on a `String`, which should be `clone()`", + deprecation: None, + module: "strings", + }, Lint { name: "struct_excessive_bools", group: "pedantic", diff --git a/tests/ui/deprecated.rs b/tests/ui/deprecated.rs index 4cbc5630d75..e1ee8dbca2c 100644 --- a/tests/ui/deprecated.rs +++ b/tests/ui/deprecated.rs @@ -1,5 +1,3 @@ -#[warn(clippy::str_to_string)] -#[warn(clippy::string_to_string)] #[warn(clippy::unstable_as_slice)] #[warn(clippy::unstable_as_mut_slice)] #[warn(clippy::misaligned_transmute)] diff --git a/tests/ui/deprecated.stderr b/tests/ui/deprecated.stderr index a348d01d734..edbb891afe0 100644 --- a/tests/ui/deprecated.stderr +++ b/tests/ui/deprecated.stderr @@ -1,88 +1,76 @@ -error: lint `clippy::str_to_string` has been removed: `using `str::to_string` is common even today and specialization will likely happen soon` - --> $DIR/deprecated.rs:1:8 - | -LL | #[warn(clippy::str_to_string)] - | ^^^^^^^^^^^^^^^^^^^^^ - | - = note: `-D renamed-and-removed-lints` implied by `-D warnings` - -error: lint `clippy::string_to_string` has been removed: `using `string::to_string` is common even today and specialization will likely happen soon` - --> $DIR/deprecated.rs:2:8 - | -LL | #[warn(clippy::string_to_string)] - | ^^^^^^^^^^^^^^^^^^^^^^^^ - error: lint `clippy::unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7` - --> $DIR/deprecated.rs:3:8 + --> $DIR/deprecated.rs:1:8 | LL | #[warn(clippy::unstable_as_slice)] | ^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: `-D renamed-and-removed-lints` implied by `-D warnings` error: lint `clippy::unstable_as_mut_slice` has been removed: ``Vec::as_mut_slice` has been stabilized in 1.7` - --> $DIR/deprecated.rs:4:8 + --> $DIR/deprecated.rs:2:8 | LL | #[warn(clippy::unstable_as_mut_slice)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: lint `clippy::misaligned_transmute` has been removed: `this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr` - --> $DIR/deprecated.rs:5:8 + --> $DIR/deprecated.rs:3:8 | LL | #[warn(clippy::misaligned_transmute)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: lint `clippy::unused_collect` has been removed: ``collect` has been marked as #[must_use] in rustc and that covers all cases of this lint` - --> $DIR/deprecated.rs:6:8 + --> $DIR/deprecated.rs:4:8 | LL | #[warn(clippy::unused_collect)] | ^^^^^^^^^^^^^^^^^^^^^^ error: lint `clippy::invalid_ref` has been removed: `superseded by rustc lint `invalid_value`` - --> $DIR/deprecated.rs:7:8 + --> $DIR/deprecated.rs:5:8 | LL | #[warn(clippy::invalid_ref)] | ^^^^^^^^^^^^^^^^^^^ error: lint `clippy::into_iter_on_array` has been removed: `this lint has been uplifted to rustc and is now called `array_into_iter`` - --> $DIR/deprecated.rs:8:8 + --> $DIR/deprecated.rs:6:8 | LL | #[warn(clippy::into_iter_on_array)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^ error: lint `clippy::unused_label` has been removed: `this lint has been uplifted to rustc and is now called `unused_labels`` - --> $DIR/deprecated.rs:9:8 + --> $DIR/deprecated.rs:7:8 | LL | #[warn(clippy::unused_label)] | ^^^^^^^^^^^^^^^^^^^^ error: lint `clippy::regex_macro` has been removed: `the regex! macro has been removed from the regex crate in 2018` - --> $DIR/deprecated.rs:10:8 + --> $DIR/deprecated.rs:8:8 | LL | #[warn(clippy::regex_macro)] | ^^^^^^^^^^^^^^^^^^^ error: lint `clippy::drop_bounds` has been removed: `this lint has been uplifted to rustc and is now called `drop_bounds`` - --> $DIR/deprecated.rs:11:8 + --> $DIR/deprecated.rs:9:8 | LL | #[warn(clippy::drop_bounds)] | ^^^^^^^^^^^^^^^^^^^ error: lint `clippy::temporary_cstring_as_ptr` has been removed: `this lint has been uplifted to rustc and is now called `temporary_cstring_as_ptr`` - --> $DIR/deprecated.rs:12:8 + --> $DIR/deprecated.rs:10:8 | LL | #[warn(clippy::temporary_cstring_as_ptr)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: lint `clippy::panic_params` has been removed: `this lint has been uplifted to rustc and is now called `panic_fmt`` - --> $DIR/deprecated.rs:13:8 + --> $DIR/deprecated.rs:11:8 | LL | #[warn(clippy::panic_params)] | ^^^^^^^^^^^^^^^^^^^^ -error: lint `clippy::str_to_string` has been removed: `using `str::to_string` is common even today and specialization will likely happen soon` +error: lint `clippy::unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7` --> $DIR/deprecated.rs:1:8 | -LL | #[warn(clippy::str_to_string)] - | ^^^^^^^^^^^^^^^^^^^^^ +LL | #[warn(clippy::unstable_as_slice)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^ -error: aborting due to 14 previous errors +error: aborting due to 12 previous errors diff --git a/tests/ui/deprecated_old.rs b/tests/ui/deprecated_old.rs index 2e5c5b7ead1..e89dca4fcfd 100644 --- a/tests/ui/deprecated_old.rs +++ b/tests/ui/deprecated_old.rs @@ -1,5 +1,3 @@ -#[warn(str_to_string)] -#[warn(string_to_string)] #[warn(unstable_as_slice)] #[warn(unstable_as_mut_slice)] #[warn(misaligned_transmute)] diff --git a/tests/ui/deprecated_old.stderr b/tests/ui/deprecated_old.stderr index ff3e9e8fcf3..2fe1facf0c7 100644 --- a/tests/ui/deprecated_old.stderr +++ b/tests/ui/deprecated_old.stderr @@ -1,40 +1,28 @@ -error: lint `str_to_string` has been removed: `using `str::to_string` is common even today and specialization will likely happen soon` - --> $DIR/deprecated_old.rs:1:8 - | -LL | #[warn(str_to_string)] - | ^^^^^^^^^^^^^ - | - = note: `-D renamed-and-removed-lints` implied by `-D warnings` - -error: lint `string_to_string` has been removed: `using `string::to_string` is common even today and specialization will likely happen soon` - --> $DIR/deprecated_old.rs:2:8 - | -LL | #[warn(string_to_string)] - | ^^^^^^^^^^^^^^^^ - error: lint `unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7` - --> $DIR/deprecated_old.rs:3:8 + --> $DIR/deprecated_old.rs:1:8 | LL | #[warn(unstable_as_slice)] | ^^^^^^^^^^^^^^^^^ + | + = note: `-D renamed-and-removed-lints` implied by `-D warnings` error: lint `unstable_as_mut_slice` has been removed: ``Vec::as_mut_slice` has been stabilized in 1.7` - --> $DIR/deprecated_old.rs:4:8 + --> $DIR/deprecated_old.rs:2:8 | LL | #[warn(unstable_as_mut_slice)] | ^^^^^^^^^^^^^^^^^^^^^ error: lint `misaligned_transmute` has been removed: `this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr` - --> $DIR/deprecated_old.rs:5:8 + --> $DIR/deprecated_old.rs:3:8 | LL | #[warn(misaligned_transmute)] | ^^^^^^^^^^^^^^^^^^^^ -error: lint `str_to_string` has been removed: `using `str::to_string` is common even today and specialization will likely happen soon` +error: lint `unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7` --> $DIR/deprecated_old.rs:1:8 | -LL | #[warn(str_to_string)] - | ^^^^^^^^^^^^^ +LL | #[warn(unstable_as_slice)] + | ^^^^^^^^^^^^^^^^^ -error: aborting due to 6 previous errors +error: aborting due to 4 previous errors diff --git a/tests/ui/str_to_string.rs b/tests/ui/str_to_string.rs new file mode 100644 index 00000000000..08f73402518 --- /dev/null +++ b/tests/ui/str_to_string.rs @@ -0,0 +1,7 @@ +#![warn(clippy::str_to_string)] + +fn main() { + let hello = "hello world".to_string(); + let msg = &hello[..]; + msg.to_string(); +} diff --git a/tests/ui/str_to_string.stderr b/tests/ui/str_to_string.stderr new file mode 100644 index 00000000000..b1f73eda5d2 --- /dev/null +++ b/tests/ui/str_to_string.stderr @@ -0,0 +1,19 @@ +error: `to_string()` called on a `&str` + --> $DIR/str_to_string.rs:4:17 + | +LL | let hello = "hello world".to_string(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: `-D clippy::str-to-string` implied by `-D warnings` + = help: consider using `.to_owned()` + +error: `to_string()` called on a `&str` + --> $DIR/str_to_string.rs:6:5 + | +LL | msg.to_string(); + | ^^^^^^^^^^^^^^^ + | + = help: consider using `.to_owned()` + +error: aborting due to 2 previous errors + diff --git a/tests/ui/string_to_string.rs b/tests/ui/string_to_string.rs new file mode 100644 index 00000000000..4c66855f709 --- /dev/null +++ b/tests/ui/string_to_string.rs @@ -0,0 +1,7 @@ +#![warn(clippy::string_to_string)] +#![allow(clippy::redundant_clone)] + +fn main() { + let mut message = String::from("Hello"); + let mut v = message.to_string(); +} diff --git a/tests/ui/string_to_string.stderr b/tests/ui/string_to_string.stderr new file mode 100644 index 00000000000..1ebd17999bd --- /dev/null +++ b/tests/ui/string_to_string.stderr @@ -0,0 +1,11 @@ +error: `to_string()` called on a `String` + --> $DIR/string_to_string.rs:6:17 + | +LL | let mut v = message.to_string(); + | ^^^^^^^^^^^^^^^^^^^ + | + = note: `-D clippy::string-to-string` implied by `-D warnings` + = help: consider using `.clone()` + +error: aborting due to previous error +